Angle adjusting device

ABSTRACT

A ratchet gear is provided to each of a pair of arms (rotors), which are coupled through a bolt, at counter surfaces of a pair of their respective rotary portions opposing in an axial direction of the bolt serving as an axis of relative rotation, and each ratchet gear is provided with a plurality of gear teeth, while both the arms are pushed in their opposing direction by a spring, so that a relative rotating position of the arms is adjusted step by step per an angle set in accordance with the gear teeth, whereby it is possible to provide a rigid angle adjusting device that can be assembled at a low cost without increasing the size.

TECHNICAL FIELD

The present invention relates to an angle adjusting device for adjustinga tilting angle of a backrest portion of a legless chair or a foldablebed, for example.

BACKGROUND ART

In an easy-to-carry foldable bed folded into three by folding down thebackrest portion and footrest portion over the seat portion, forexample, each of the frames respectively forming the backrest portionand footrest portion is coupled to the frame of the seat portion throughan angle adjusting device, whereby it is possible to adjust tiltingangles of the backrest portion and footrest portion with respect to theseat portion.

As is disclosed in Japanese Utility Model Publication No. 59-20118 filedby the inventors of the present application, for example, such an angleadjusting device is provided with coupling portions each coupled to therespective tip end portions of the two frames respectively forming, forexample, the seat portion and backrest portion.

The coupling portion at the seat portion side commonly used as thestationary side is provided with a pair of disc portions with theirthickness direction directed to the width direction of the foldable bed,and the coupling portion at the backrest portion side commonly used asthe movable side coaxially supports a spur ratchet gear placed with itsthickness direction directed to the width direction of the foldable bed.

Also, a hook of ratchet supported somewhere between the pair of discportions is allowed to move around the axis in the width direction ofthe foldable bed, and pushed by a spring in a direction such that theratchet engages with the gear teeth of a ratchet gear.

Each of the gear teeth has a tapered surface such that presses theratchet against the spring in association with a rotation of the ratchetgear when the backrest portion is folded, so that the engagement withthe ratchet can be released. However, once the ratchet reaches theadjacent gear tooth, the ratchet constantly pushed by the spring engageswith that gear tooth again. Also, each of the gear teeth has a surfaceof a shape such that maintains the engagement with the ratchet inassociation with a rotation of the ratchet gear when the backrestportion is unfolded.

Hence, a tilting angle of the backrest portion can be changed as onedesires in the folding direction, whereas the tilting angle of thebackrest portion in the unfolding direction with respect to the seatportion can be changed step by step in accordance with the gear teethbecause the ratchet is locked.

Here, the angle adjusting device as discussed above is provided withreleasing mechanism that releases the engagement between the ratchet andgear teeth by pressing the ratchet against the spring when a tiltingangle of the backrest portion in the folding direction reaches apredetermined angle. The releasing mechanism returns the ratchet andgear teeth in the initial engagement state when the backrest portion isrotated to the maximum unfolded position after the engagement isreleased.

However, the conventional angle adjusting device as discussed abovemaintains the backrest portion, for example, of the foldable bed, at apredetermined angle by engaging the ratchet with a single gear tooth ofthe ratchet gear, which raises a problem that, when one lies down on thefoldable bed, all the applied load concentrates onto the single geartooth and ratchet.

The above problem may be solved by upsizing the gear teeth and ratchet.However, this solution causes inconveniences such that the entire angleadjusting device becomes so large that it impairs one's lying comfort,etc. Also, when the gear teeth alone are upsized while maintaining thesize of the entire angle adjusting device intact, the total number ofthe teeth is reduced, which raises another problem that an adjustableangle per step becomes larger.

It may be possible to increase hardness of the gear teeth and ratchetwithout changing their respective sizes by subjecting the same tocarburization or making the same out of materials having higherhardness. However, this increases the manufacturing costs, which posesanother problem.

The present invention is devised to solve the above problems and has anobject to provide a rigid angle adjusting r, which can be assembled at alow cost without increasing the size by providing a plurality ofengaging portions to a pair of rotors that relatively rotate around theaxis of rotation on their respective counter surfaces opposing in adirection along the axis of rotation, and pushing the rotors in anopposing direction by a spring so as to maintain the engagement of theengaging portions on the rotors.

SUMMARY OF THE INVENTION

An angle adjusting device of the present invention is an angle adjustingdevice capable of adjusting a relative rotating position of a pair ofrotors coupled through an axis of rotation step by step, the deviceincluding: a plurality of engaging portions provided on surfaces of thepair of rotors opposing in a direction along the axis of rotation; and aspring for pushing the pair of rotors in an opposing direction.

According to the invention, it is arranged such that a plurality ofengaging portions are provided to a pair of rotors that relativelyrotate around the axis of rotation on their respective counter surfacesopposing in a direction along the axis of rotation, and a spring forpushing the rotors in an opposing direction is provided to maintain theengagement between the rotors. Consequently, it is possible to readilyassemble a rigid and compact angle adjusting device that develops aquite large engaging strength by engaging at the plurality of engagingportions.

The angle adjusting device of the present invention can be attached to afoldable bed, a legless chair, etc. as discussed above through couplingportions that will be described below. It should be appreciated,however, that the application is not limited to the foldable bed,legless chair, etc., and the angle adjusting device can be employed inother products that need angle adjustment. Also, the angle adjustingdevice does not have to be attached to the foldable bed, legless chair,etc. through the coupling portion, and can be attached to the same atthe rotors either directly or indirectly.

Another angle adjusting device of the present invention is characterizedby further including a releasing body placed concentrically somewherebetween the pair of rotors, wherein the releasing body allows engagementbetween the pair of rotors when placed at a first rotating position withrespect to either one of the pair of rotors, and releases the engagementby moving the pair of rotors apart from each other when placed at asecond rotating position.

According to the invention, it is arranged such that a releasing body isplaced concentrically somewhere between the pair of rotors, and thereleasing body allows engagement between the pair of rotors when placedat the first rotating position with respect to either one of the pair ofrotors, and releases the engagement by moving the pair of rotors apartfrom each other when placed at the second rotating position.Consequently, it is possible to provide releasing mechanism for theengagement of the angle adjusting device as discussed above by a simplearrangement.

Still another angle adjusting device of the present invention ischaracterized in that: one of the either one of the rotors and thereleasing body is provided with a convex portion on a counter surfaceopposing the other; and the other is provided with, on a counter surfaceopposing a counterpart, a concave portion that engages with the convexportion when the releasing body is placed at the first rotatingposition, the convex portion moving one of the either one of the rotorsand the releasing body apart from the other by touching the countersurface of the other except for the concave portion when the releasingbody is placed at the second rotating position.

According to the invention, it is arranged such that one of the eitherone of the rotors and the releasing body is provided with a convexportion on a counter surface opposing the other, and the other isprovided with, on a counter surface opposing a counterpart, a concaveportion that engages with the convex portion when the releasing body isplaced at the first rotating position, the convex portion moving one ofthe either one of the rotors and the releasing body apart from the otherby touching the counter surface of the other except for the concaveportion when the releasing body is placed at the second rotatingposition. Consequently, when the releasing body is at the first rotatingposition, the convex portion fits into the concave portion and thereleasing body is in a state described as, for example, closely adheringto the either one of the rotors, whereby the pair of rotors engage witheach other. On the other hand, when the releasing body is at the secondrotating position, the convex portion touches the counter surface of theother except for the concave portion, whereby the either one of therotors and the releasing body that have been in the above closelyadhering state are moved apart relatively from each other. Consequently,the either one of the rotors and the other rotor are spaced apart fromeach other, thereby making it possible to release the engagement asdiscussed above.

Still another angle adjusting device of the present invention ischaracterized in that the releasing body is provided with two contactportions spaced apart by a predetermined distance in a direction of arelative rotation with respect to the other rotor, and the other rotoris provided with a moving portion that moves between the two contactportions in association with a relative rotation with respect to thereleasing body, the moving portion allowing the releasing body to rotateto the first and second rotating positions with respect to the eitherone of the rotors by touching the two contact portions, respectively.

According to the invention, it is arranged such that the releasing bodyis provided with two contact portions spaced apart by a predetermineddistance in a direction of a relative rotation with respect to the otherrotor, and the other rotor is provided with a moving portion that movesbetween the two contact portions in association with a relative rotationwith respect to the releasing body, the moving portion allowing thereleasing body to rotate to the first and second rotating positions withrespect to the either one of the rotors by touching the two contactportions, respectively. Consequently, it is possible to readily achieverotating mechanism of the releasing body as discussed above.

Still another angle adjusting device of the present invention ischaracterized in that the axis of rotation is composed of a rivet.

According to the invention, it is arranged such that the axis ofrotation that couples the pair of rotors is composed of a rivet.Consequently, the dimension of the entire angle adjusting device in adirection along the axis of rotation can be made compact.

Still another angle adjusting device of the present invention ischaracterized in that the spring is a spiral spring.

According to the invention, it is arranged such that the spring is aspiral spring. Consequently, the dimension of the entire angle adjustingdevice in the direction along the axis of rotation can be made morecompact. Here, a conical spring made of a wire material, a volute springmade out of a plate material, etc. can be used as the spiral spring.

Still another angle adjusting device of the present invention ischaracterized in that each of the engaging portions is shaped into atriangle including the counter surface of either rotor where each isprovided when seen on a cross section in a radius direction of arotation of the rotor, and either one of side portions of the triangleother than a side on the counter surface of either rotor engages with acorresponding side portion of the engaging portion on the other rotor.

According to the invention, it is arranged such that each of theengaging portions is shaped into a triangle including the countersurface of either rotor where each is provided when seen on a crosssection in a radius direction of a rotation of the rotor, and either oneof side portions of the triangle other than a side on the countersurface of either rotor engages with a corresponding side portion of theengaging portion on the other opposing rotor. Consequently, it ispossible to shape each engaging portion into a quite simple triangletooth.

Still another angle, adjusting device of the present invention ischaracterized in that the either one of side portions is titled by apredetermined angle toward an engaging direction from the opposingdirection.

According to the invention, the either one of side portions is shapedinto a serration by giving a tilt of a predetermined angle toward anengaging direction from the opposing direction. Hence, when a force isapplied in a direction of a relative rotation of the rotors to maintaintheir engagement, in order to release the engagement by moving therotors apart from each other, it is necessary to separate the rotorsfrom each other by forcing each rotor to rotate relatively in adirection against the above force. Consequently, it is possible tomaintain the engagement so as not to be released accidentally.

Still another angle adjusting device of the present invention ischaracterized in that each of the engaging portions is formed by cuttingand bending a part of either rotor where each is provided.

According to the invention, it is arranged such that each of theengaging portions is formed by cutting and bending a part of the rotor.Consequently, it is possible to readily form the engaging portions as anintegral part of the rotor commonly formed out of a metal plate.

Still another angle adjusting device of the present invention ischaracterized in that the plurality of engaging portions are aligned inmore than one line at different positions in a diameter direction ofeach rotor where the plurality of engaging portions are provided.

According to the invention, it is arranged such that the engagingportions are aligned in more than one line at different positions in adiameter direction of the rotor. Consequently, because a larger numberof engaging portions can be provided, the adjustment can be carried outstep by step with a smaller angle.

Still another angle adjusting device of the present invention ischaracterized in that different intervals are given to the plurality ofengaging portions in a direction of a rotation between the pair ofrotors opposing each other.

According to the invention, it is arranged such that different intervalsare given to the engaging portions in a circumferential direction of arotation between the pair of rotors. Consequently, even when fewerengaging portions are provided, it is possible to carry out theadjustment in every angle set according to the greatest common divisorof isometric angles of the engaging portions on each rotor.

Still another angle adjusting device of the present invention ischaracterized in that at least one of the pair of rotors is providedwith a coupling portion for coupling to a bar-wise or tube-wise member.

According to the invention, it is arranged such that at least one of thepair of rotors is provided with a coupling portion for coupling to abar-wise or tube-wise member. Consequently, the coupling portion can bereadily coupled to the frames of a legless chair, a foldable bed, forexample.

Still another angle adjusting device of the present invention ischaracterized in that the coupling portion is cylindrical.

According to the invention, because it is arranged such that thecoupling portion is cylindrical, the coupling portion can be coupled tothe frames more readily by fitting the former into the latter.

Still another angle adjusting device of the present invention ischaracterized in that at least one of the pair of rotors is formed as anintegral part of the coupling portion.

According to the invention, it is arranged such that at least one of thepair of rotors is formed as an integral part of the coupling portion.Consequently, the angle adjusting device can be assembled at a low costby making these components out of a plate of metal, for example.

Still another angle adjusting device of the present invention ischaracterized in that at least one of the pair of rotors and theplurality of engaging portions are formed out of synthetic resin as onebody.

According to the invention, because it is arranged such that the rotorand engaging portions are formed out of synthetic resin as one body, theangle adjusting device can be assembled at a lower cost.

Still another angle adjusting device of the present invention ischaracterized in that at least one of the pair of rotors is providedwith a cover that covers, either partially or entirely, the plurality ofengaging portions from an outside in a radius direction of a rotation.

According to the invention, it is arranged such that at least one of thepair of rotors is provided with a cover that covers the engagingportions from an outside in a radius direction of a rotation.Consequently, it is possible to prevent unwanted intrusion of dust intothe engaging surfaces of the engaging portions or the like from theoutside.

A further angle adjusting device of the present invention ischaracterized in that at least one of the pair of rotors and the coverare formed as one body.

According to the invention, it is arranged such that the aforementionedcover and at least one of the pair of rotors are formed as one body.Consequently, it is possible to assemble an angle adjusting deviceequipped with such a cover at a lower cost.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is an exploded perspective view showing an arrangement of a firstembodiment of an angle adjusting device according to the presentinvention;

FIG. 2 are plan views respectively showing an arrangement of one of twoarms and an arrangement of a releasing body of the angle adjustingdevice shown in FIG. 1;

FIG. 3 are top views of the arms of the angle adjusting device shown inFIG. 1;

FIG. 4 are explanatory views explaining an operation of the angleadjusting device according to the present invention;

FIG. 5 are explanatory views explaining an operation of the angleadjusting device according to the present invention;

FIG. 6 are explanatory views explaining an operation of the angleadjusting device according to the present invention;

FIG. 7 are explanatory views explaining an operation of the angleadjusting device according to the present invention;

FIG. 8 are top views showing a second embodiment of the angle adjustingdevice according to the present invention;

FIG. 9 are views showing a third embodiment of the angle adjustingdevice according to the present invention;

FIG. 10 are views showing a fourth embodiment of the angle adjustingdevice according to the present invention;

FIG. 11 are views showing a fifth embodiment of the angle adjustingdevice according to the present invention; and

FIG. 12 are views showing a sixth embodiment of the angle adjustingdevice according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description will describe in detail the present inventionwith reference to accompanying drawings in which embodiments of theinvention are illustrated.

First Embodiment

FIG. 1 is an exploded perspective view showing an arrangement of a firstembodiment of an angle adjusting device according to the presentinvention. The angle adjusting device of the present embodiment includesa pair of arms 1 and 2, a releasing body 3, a bolt 4, a nut 5, and aspring 6 composed of a coil spring, and for use, the arms 1 and 2 arerespectively joined to where they should be coupled to, for example, apair of frames in a foldable bed.

Each of the arms 1 and 2 is formed out of a plate of metal into analmost P shape when seen in one plane. In each P shape, the top (larger)portion forms a rotary portion 10/20 as a disc of rotor, and the bottom(smaller) portion forms a strip of coupling portion 11/21.

For ease of explanation, in FIG. 1, each of the arms 1 and 2 is placedwith the rotary portion 10/20 that protrudes toward the lateral side ofthe P shape (the width direction of the coupling portion 11/21) facingupward and the coupling portion 11/21 at a horizontal position.

Also, of the two arms, the arm 1 is placed with the top end of itscoupling portion 11 facing to the left side, and the other arm 2 isplaced in front of the arm 1 with the top end of its coupling portion 21facing to the right side, which state being defined as the initialstate.

A through hole 12 for the bolt 4 serving as the axis of rotation is madethrough at the center of the rotary portion 10 of the arm 1. Also, aratchet gear 13 is formed along a part of the peripheral portion of thefront side surface of the rotary portion 10 in the circumferentialdirection as a plurality of engaging portions.

Each gear tooth 13 a is shaped into a spike with its trough portiondirected to the radius direction of the rotary portion 10. Also, acontrol pin 14 as a moving portion is provided at the inner radialposition of the ratchet gear 13 in such a manner so as to protrudefrontward.

FIG. 2 are plan views respectively showing the arrangement of the arm 2as one of the arms and the arrangement of the releasing body 3 of theangle adjusting device shown in FIG. 1, and each shows a state when seenfrom the inward (from the bolt 4 side). As is shown in FIG. 2(a), therotary portion 20 of the arm 2 is provided with a through hole 22 and aratchet gear 23 in the same manner as the arm 1. Also, a slit 24 ofapproximately 120° long in the circumferential direction is provided tothe inner side surface of the rotary portion 20 at a positioncorresponding to the control pin 14 provided on the arm 1. Further,three pit holes 25's adequately spaced apart in the circumferentialdirection are made through the rotary portion 20 as concave portions,and releasing pin 26 as a convex portion is provided to each pit hole 25at the same angular, position (approximately 20°) in thecounterclockwise direction in FIGS. 2.

Also, as is shown in FIG. 2(b), the releasing body 3 is substantially adisc, and provided with a cutout portion 31 by cutting out theperipheral portion for approximately 100° long in the circumferentialdirection. Also, a through hole 32 for the bolt 4 is made through at thecenter portion of the releasing body 3. Further, the releasing body 3 isprovided with three pit holes 33's at positions respectivelycorresponding to the three releasing pins 26's provided on the arm 2 asrecess into which the releasing pins 26 respectively fit, and threereleasing pins 34's at positions respectively corresponding to the threepit holes 25's on the arm 2 side as convex portions.

The device has components each arranged in the above manner, and isassembled by inserting the bolt 4 through the releasing body 3, arm 2,and spring 6 sequentially from the arm 1 side and tightening the nut 5with an adequate force (see FIG. 4).

FIG. 3 are top views of the arms 1 and 2 of the angle adjusting deviceshown in FIG. 1. FIG. 3(a) shows the arm 2 alone, and FIG. 3(b) shows astate when the arms 1 and 2 are joined.

As is shown in FIG. 3(a), the ratchet gear 23 of the arm 2 has spikes ofgear teeth 23 a, each of which being shaped into a right triangle ornearly a right triangle when seen in the radius direction of the rotaryportion 20, and all the gear teeth 23 a's are directed to one directionso that the upright side of each gear tooth 23 a at the uppercircumference position is on the right side of FIG. 2 when seen fromabove.

Also, as is shown in FIG. 3(b), each gear tooth 13 a on the arm 1 sideis formed in the same manner as above when the arm 1 is placed in thesame direction as the arm 2. Hence, as is shown in FIG. 3(b), theratchet gears 13 and 23 mesh with each other exactly when the arms 1 and2 are joined oppositely.

By subjecting each gear tooth 13 a to hardening, it is possible toincrease the hardness thereof as has been discussed above. For example,the hardness can be increased by approximately 30% by means ofcarburization.

FIGS. 4 through 7 are explanatory views explaining operations of theangle adjusting device according to the present invention. FIGS. 4(a),5(a), 6(a), and 7(a) show the angle adjusting device seen from thefront, and the nut 5 and spring 6 are omitted from these drawings forease of understanding. Also, FIGS. 4(b), 5(b), 6(b), and 7(b) arelongitudinal cross sections of FIGS. 4(a), 5(a), 6(a), and 7(a),respectively.

As is shown in FIG. 4, the control pin 14 is positioned in the vicinityof the bottom of the rotary portion 10 in the circumferential direction,and in the initial state, the control pin 14 touches the slit 24 of therotary portion 20 at the end portion in the counterclockwise direction(in FIG. 4), as well as the cutout portion 31 of the releasing body 3 atan end portion 31 a in the counterclockwise direction (in FIG. 4) as oneof the contact portions.

Also, as has been discussed above, each of the releasing pins 26's onthe arm 2 side fits into their respective pit holes 33's on thereleasing body 3 side, and each of the releasing pins 34's on thereleasing body 3 fits into their respective pit holes 25's on the arm 2side. Hence, under these conditions, as is shown in FIG. 4(b), therotary portion 20 of the arm 2 pushed toward the arm 1 by the spring 6adheres to the rotary portion 10 almost completely through the releasingbody 3 with its ratchet gear 23 touching the ratchet gear 13 of therotary portion 10.

Under the conditions shown in FIG. 4, the ratchet gear 13 on the arm 1side and the ratchet gear 23 on the arm 2 side mesh and engage with eachother, so that the arm 2 side is not allowed to rotate in a clockwisedirection with respect to the arm 1 side serving as the stationary sideby using the bolt 4 as the axis of rotation, for example.

On the other hand, as the arm 2 rotates in the counterclockwisedirection, the ratchet gears 13 and 23 push the arm 2 against thepushing force of the spring 6 in a direction to be spaced apart from thearm 1 in such a manner that each mounts onto their respective engaginggear teeth 13 a and 23 a along the slopes thereof, whereby theengagement of the ratchet gears 13 and 23 is released.

As a result, the arm 2 starts to rotate in the counterclockwisedirection, but is pushed by the spring 6 again when it reaches theadjacent gear teeth 13 a and 23 a, whereupon the arm 2 is placed in thestate shown in FIG. 5.

In this manner, it is arranged such that the rotating position of thearm 2 with respect to the arm 1 can be adjusted per angle at which thegear teeth 13 a and 23 a are formed as are shown in FIG. 5 and FIG. 6,and the releasing body 3 engaged at the pit holes 25's and releasingpins 26's of the rotary portion 20 rotates in association with therotary portion 20 of the rotating arm 2. Here, this relative rotatingposition of the releasing body 3 with respect to the rotary portion 20is defined as a first rotating position.

Then, as is shown in FIG. 7, an end portion 31 b of the cutout portion31 of the releasing body 3 in the clockwise direction touches thecontrol pin 14 on the arm 1 when the arm 2 has rotated by approximately100° from the initial state shown in FIG. 5, whereupon the rotation ofthe releasing body 3 in this direction is locked. It should beappreciated, however, that the arm 2 is allowed to rotate further byapproximately 20° until the control pin 14 on the arm 1 touches the endportion of the slit 24 in the clockwise direction.

This displacement of approximately 20° in the rotating positions betweenthe arm 2 and releasing body 3, in other words, allowing the releasingbody 3 to rotate with respect to the rotary portion 20 on the arm 2 sideup to a second rotating position that is different from the firstrotating position, permits the releasing pins 26's on the arm 2 to mountonto the releasing pins 34's on the releasing body 3, whereby the arm 2is pushed against the spring 6 in a direction to be spaced apart fromthe arm 1, thereby releasing the engagement between the ratchet gears 13and 23.

Strictly speaking, each of the releasing pins 34's on the releasing body3 side is a spike with its top depressed rather than a pin, and the tipend of the corresponding releasing pin 26 on the arm 2 side fits intothe depressed portion, thereby making it possible to maintain thereleased state of the engagement.

Further, under the released state, the releasing body 3 rotates inassociation with a rotation of the arm 2 in the clockwise direction, andthe end portion 31 a of the cutout portion 31 of the releasing body 3 inthe counterclockwise direction touches the control pin 14 on the arm 1when the releasing body 3 has rotated by approximately 100°, whereupon afurther rotation of the releasing body 3 in this direction is locked. Itshould be appreciated, however, that the arm 2 is allowed to rotatefurther by approximately 20° until the control pin 14 on the arm 1touches the end portion of the slip 24 in the counterclockwisedirection.

This displacement of approximately 20° in the rotating positions betweenthe arm 2 and releasing body 3 dismounts the releasing pins 26's on thearm 2 side that have mounted onto the releasing pins 34's on thereleasing body 3 side, whereby the releasing pins 26's and 34's on eachside fit into their respective pit holes 33's and 25's on the countersides, thereby allowing the arm 2 and releasing body 3 to return to theinitial state shown in FIG. 4.

The present embodiment showed the arrangement where the ratchet gears 13and 23 are formed partially on the circumferences of the rotary portions10 and 20, respectively. It should be appreciated, however, that theratchet gears 13 and 23 may be formed on the entire circumferences,which ensures the strength of holding the rotating position of each ofthe arms 1 and 2.

Second Embodiment

FIG. 8 are top views showing a second embodiment of the angle adjustingdevice according to the present invention, and show the top views of thearms 1 and 2. FIG. 8(a) shows the arm 2 alone and FIG. 8(b) shows astate when the arms 1 and 2 are joined. In the present embodiment, thegear teeth 13 a and 23 a respectively formed on the arms 1 and 2 areformed as serrations when seen in the radius direction of the rotaryportions 10 and 20, and a tilt of a predetermined angle is given to eachin the engaging direction.

According to the above arrangement, when one tries to rotate the arm 2in the clockwise direction with a quite large force under the stateshown in FIG. 5 or FIG. 6, for example, it is possible to reduce thepossibility of releasing the engagement between the ratchet gears 13 and23 in mesh with each other against the pushing force of the sprig 6.However, if a too large tilting angle is given, it becomes difficult torelease the engagement between the ratchet gears 13 and 23 whennecessary, and for this reason, the preferable tilting angle isapproximately two to three degrees.

The other arrangements and functions of the angle adjusting device ofthe present embodiment are identical with those of the counterpart ofthe first embodiment. Thus, like components are labeled with likenumerals and the detailed explanation is not repeated for ease ofexplanation.

Third Embodiment

FIG. 9 are views showing a third embodiment of the angle adjustingdevice according to the present invention. FIG. 9(a) is a plan view ofthe arm 2 seen from the front, FIG. 9(b) is a top view of the arm 2, andFIG. 9(c) is a top view showing a state when the arms 1 and 2 arejoined.

In the present embodiment, the ratchet gears 13 and 23 respectivelyprovided on the arms 1 and 2 are formed in the following manner.

The peripheral portion of each of the rotary portions 10 and 20 is cutin L shapes, and the cut tab-wise portions are pushed outward, so thatthe tip end portions of the pushed out side form each of the gear teeth13 a and 23 a.

Forming each of the gear teeth 13 a and 23 a in the above manner makesit possible to readily form the ratchet gears 13 and 23 respectivelyfrom the arms 1 and 2 each made out of a plate member.

However, as shown in FIG. 9(c), each of the gear teeth 13 a and 23 aformed in the above manner has a slope tilted in a direction (engageddirection) opposite to the one shown in the second embodiment.Nevertheless, the tilting angle is too small to cause the engagement tobe released upon application of a load to some extent as has beendiscussed above.

The other arrangements and functions of the angle adjusting device ofthe present embodiment are identical with those of the counterpart ofthe first embodiment. Thus, like components are labeled with likenumerals and the detailed explanation is not repeated for ease ofexplanation.

Fourth Embodiment

FIG. 10 are views showing a fourth embodiment of the angle adjustingdevice according to the present invention. FIG. 10(a) is a plan viewshowing the arm 1 seen from the front, FIG. 10(b) is a plan view showingthe arm 2 seen from the front, and FIG. 10(c) is a top view showing astate when the arms 1 and 2 are joined.

In the present embodiment, the gear teeth 13 a and 23 a respectivelyprovided on the arms 1 and 2 are formed in the following manner.

The peripheral portion of each of the rotary portions 10 and 20 is cutin square cornered C shapes at the slightly inner radial positions, andthe cut tab-wise portions are pushed outward, so that the tip endportions of the pushed out side form each of the gear teeth 13 a and 23a.

Forming each of the gear teeth 13 a and 23 a in the above manner makesit possible to readily form the gear teeth 13 a and 23 a respectivelyfrom the arms 1 and 2 each made out of a plate member.

As is in the third embodiment, each of the gear teeth 13 a and 23 aformed in the above manner has a slope tilted in the engaged direction.However, the tilting angle is too small to cause the engagement to bereleased upon application of a load to some extent as has been discussedabove.

Also, the gear teeth 13 a and 23 a of the present embodiment areprovided at different pitches in the circumferential directions on thearms 1 and 2, respectively. For example, as is shown in FIG. 10(a), sixgear teeth 13 a are provided on the arm 1 side at an interval ofapproximately 60°, and as is shown in FIG. 10(b), nine gear teeth 23 aare provided on the arm 2 side at an interval of approximately 40°.

By adapting the arrangement discussed above, compared with thearrangements of the first through third embodiments such that allow theangle adjustment in steps as many as the number of the gear teeth 13 aand 23 a, the angle adjustment is allowed per greatest common divisor ofthe pitch angles of all the gear teeth 13 a and 23 a, that isapproximately 20° (18 steps).

It should be appreciated, however, that, as is shown in FIG. 10(c),according to the above arrangement, only three of the gear teeth 13 aand 23 a are in mesh at one time, and not all the gear teeth 13 a and 23a mesh with each other simultaneously, which lowers the strength ofholding the rotating position of each of the arms 1 and 2. However, adesired holding strength can be secured by increasing the number of thegear teeth 13 a and 23 a as necessary.

The other arrangements and functions of the angle adjusting device ofthe present embodiment are identical with those of the counterpart ofthe first embodiment. Thus, like components are labeled with likenumerals and the detailed explanation is not repeated for ease ofexplanation.

Fifth Embodiment

FIG. 11 are views showing a fifth embodiment of the angle adjustingdevice of the present invention. FIG. 11(a) is a plan view showing thearm 1 seen from the front and FIG. 11(b) is a plan view showing the arm2 seen from the front.

In the present embodiment, the gear teeth 13 a and 23 a respectivelyprovided on the arms 1 and 2 are formed in the following manner.

Each of the gear teeth 13 a and 23 a are formed in the same manner asthe fourth embodiment except that a plurality of gear teeth 13 a and 23a are formed in two lines in the radius direction of the rotary portions10 and 20 of the arms 1 and 2, respectively. For example, six gear teeth13 a and six gear teeth 23 a are respectively provided on the arms 1 and2 in the outer lines at an interval of approximately 60°, and six gearteeth 13 a and six gear teeth 23 a are respectively provided on the arms1 and 2 in the inner lines at an interval of approximately 60° atpositions shifted by approximately 30° with respect to those in theouter line, totaling in 12 gear teeth on each arm.

By adapting the above arrangement, it is possible to form the gear teeth13 a and 23 a in a total number exceeding the number attained byphysically forming each group of the gear teeth 13 a and 23 a in asingle line. In FIGS. 11, not only can the angle be adjusted byapproximately 30° in each time (12 steps), but also all the gear teeth13 a and 23 a mesh with each other simultaneously, thereby securingsatisfactory strength in holding the rotating position of each of thearms 1 and 2.

The other arrangements and functions of the angle adjusting device ofthe present embodiment are identical with those of the counterpart ofthe first embodiment. Thus, like components are labeled with likenumerals and the detailed explanation is not repeated for ease ofexplanation.

Sixth Embodiment

FIG. 12 are views showing a sixth embodiment of the angle adjustingdevice according to the present invention. FIG. 12(a) is a plan viewshowing the angle adjusting device seen from the front, and FIG. 12(b)is a bottom view of the angle adjusting device. Also, FIG. 12(c) is aside view of FIG. 12(a) seen from the left side with a portion along theline A—A being removed.

In the present embodiment, the strips of coupling portions 11 and 21 ofthe arms 1 and 2, respectively, are curved cylindrically by using thelongitudinal directions as an axial direction. By forming the couplingportions 11 and 21 in this manner, it is possible to readily couple thepipes of frames of an unillustrated foldable bed to the angle adjustingdevice by fitting the coupling portions 11 and 21 into the frames.

Two small protrusions 28's are provided to the outer circumferentialsurfaces at the end portions of the coupling portions 11 and 21 at thesides of the rotary portions 10 and 20, respectively, so that the frameshaving the coupling portions 11 and 21 fitted therein will not go downtoo deep toward the rotary portions 10 and 20.

Also, an overhang cover 29 covering the outer circumferential surface ofthe rotary portion 10 is provided at the peripheral portion of therotary portion 20. The cover 29 protects the gear teeth 13 a and 23 aprotruding in a space between the rotary portions 10 and 20 fromcontamination (dust) from the outside. Alternatively, the cover 29 maybe provided at the rotary portion 10 side or at both the rotary portions10 and 20 in double.

Also, the bolt 4 and nut 5 are replaced with a rivet 7. As a result, notonly can the dimension of the angle adjusting device in the lengthwisedirection be made compact, but also the cost can be saved.

Further, the coil spring employed as the spring 6 is replaced with aspiral spring, and as a result, the dimension of the angle adjustingdevice in the longitudinal direction can be made more compact. Besides aconical spring made of a wire material as shown in FIGS. 12, a so-calledvolute spring made out of a plate material can be used as the spiralspring.

The other arrangements and functions of the angle adjusting device ofthe present embodiment are identical with those of the counterpart ofthe first embodiment. Thus, like components are labeled with likenumerals and the detailed explanation is not repeated for ease ofexplanation.

Each of the above embodiments showed the arrangement where the arms 1and 2 are made of metal. However, the angle adjusting device of thepresent invention can employ arms 1 and 2 made of synthetic resin,because the engagement is established by a plurality of gear teeth 13 aand 23 a, which makes it possible to achieve a further cost reduction.

INDUSTRIAL APPLICABILITY

As has been discussed above, the angle adjusting device of the presentinvention is arranged such that a plurality of engaging portions areprovided to a pair of rotors that relatively rotate around the axis ofrotation on their respective counter surfaces opposing in a directionalong the axis of rotation, and a spring for pushing the rotors in anopposing direction is provided to maintain the engagement between therotors. Consequently, it is possible to readily assemble a rigid andcompact angle adjusting device that develops a quite large engagingstrength by engaging at the plurality of engaging portions.

Also, it is arranged such that a releasing body is placed concentricallysomewhere between the pair of rotors, and the releasing body allowsengagement between the pair of rotors when placed at a first rotatingposition with respect to either one of the pair of rotors, and releasesthe engagement by moving the pair of rotors apart from each other whenplaced at a second rotating position. Consequently, it is possible toprovide releasing mechanism for the engagement of the angle adjustingdevice as discussed above by a simple arrangement.

Also, it is arranged such that one of the either one of the rotors andthe releasing body is provided with a convex portion on a countersurface opposing the other, and the other is provided with, on a countersurface opposing a counterpart, a concave portion that engages with theconvex portion when the releasing body is placed at the first rotatingposition, the convex portion moving one of the either one of the rotorsand the releasing body apart from the other by touching the countersurface of the other except for the concave portion when the releasingbody is placed at the second rotating position. Consequently, when thereleasing body is at the first rotating position, the convex portionfits into the concave portion and the releasing body is in a statedescribed as, for example, closely adhering to the either one of therotors, whereby the pair of rotors engage with each other. On the otherhand, when the releasing body is at the second rotating position, theconvex portion touches the counter surface of the other except for theconcave portion, whereby the either one of the rotors and the releasingbody that have been in the above closely adhering state are moved apartrelatively from each other. Consequently, the either one of the rotorsand the other rotor are spaced apart from each other, thereby making itpossible to release the engagement as discussed above.

Also, it is arranged such that the releasing body is provided with twocontact portions spaced apart by a predetermined distance in a directionof a relative rotation with respect to the other rotor, and the otherrotor is provided with a moving portion that moves between the twocontact portions in association with a relative rotation with respect tothe releasing body, the moving portion allowing the releasing body torotate to the first and second rotating positions with respect to theeither one of the rotors by touching the two contact portions,respectively. Consequently, it is possible to readily achieve rotatingmechanism of the releasing body as discussed above.

Also, it is arranged such that the axis of rotation that couples thepair of rotors is composed of a rivet. Consequently, the dimension ofthe entire angle adjusting device in a direction along the axis ofrotation can be made compact.

Also, it is arranged such that the spring is a spiral spring.Consequently, the dimension of the entire angle adjusting device in thedirection along the axis of rotation can be made more compact. Here, aconical spring made of a wire material, a volute spring made out of aplate material, etc. can be used as the spiral spring.

Also, it is arranged such that each of the engaging portions is shapedinto a triangle including the counter surface of either rotor where eachis provided when seen on a cross section in a radius direction of arotation of the rotor, and either one of side portions of the triangleother than a side on the counter surface of either rotor engages with acorresponding side portion of the engaging portion on the other opposingrotor. Consequently, it is possible to shape each engaging portion intoa quite simple triangle tooth.

Also, the either one of side portions is shaped into a serration bygiving a tilt of a predetermined angle toward an engaging direction fromthe opposing direction. Hence, when a force is applied in a direction ofa relative rotation of the rotors to maintain their engagement, in orderto release the engagement by moving the rotors apart from each other, itis necessary to separate the rotors from each other by forcing eachrotor to rotate relatively in a direction against the above force.Consequently, it is possible to maintain the engagement so as not to bereleased accidentally.

Also, it is arranged such that each of the engaging portions is formedby cutting and bending a part of the rotor. Consequently, it is possibleto readily form the engaging portions as an integral part of the rotorcommonly formed out of a metal plate.

Also, it is arranged such that the engaging portions are aligned in morethan one line at different positions in a diameter direction of therotor. Consequently, because a larger number of engaging portions can beprovided, the adjustment can be carried out step by step with a smallerangle.

Also, it is arranged such that different intervals are given to theengaging portions in a circumferential direction of a rotation betweenthe pair of rotors. Consequently, even when fewer engaging portions areprovided, it is possible to carry out the adjustment in every angle setaccording to the greatest common divisor of isometric angles of theengaging portions on each rotor.

Also, it is arranged such that at least one of the pair of rotors isprovided with a coupling portion for coupling to a bar-wise or tube-wisemember. Consequently, the coupling portion can be readily coupled to theframes of a legless chair, a foldable bed, for example.

Also, because it is arranged such that the coupling portion iscylindrical, the coupling portion can be coupled to the frames morereadily by fitting the former into the latter.

Also, it is arranged such that at least one of the pair of rotors isformed as an integral part of the coupling portion. Consequently, theangle adjusting device can be assembled at a low cost by making thesecomponents out of a plate of metal, for example.

Also, because it is arranged such that the rotor and engaging portionsare formed out of synthetic resin as one body, the angle adjustingdevice can be assembled at a lower cost.

Also, it is arranged such that at least one of the pair of rotors isprovided with a cover that covers the engaging portions from an outsidein a radius direction of a rotation. Consequently, it is possible toprevent unwanted intrusion of dust into the engaging surfaces of theengaging portions or the like from the outside.

Further, it is arranged such that the aforementioned cover and at leastone of the pair of rotors are formed as one body. Consequently, it ispossible to assemble an angle adjusting device equipped with such acover at a lower cost. Thus, the present invention can offer the aboveand other excellent effects.

What is claimed is:
 1. An angle adjusting device capable of adjusting a relative rotating position of a pair of rotors coupled through an axis of rotation step by step, comprising: a pair of rotors; a plurality of engaging portions provided on opposing surfaces of the pair of rotors opposing in a direction along the axis of rotation; a spring for pushing the pair of rotors in an opposing direction; a releasing body placed concentrically between the pair of rotors, wherein the releasing body allows engagement between the pair of rotors when placed at a first rotating position with respect to either one of the pair of rotors, and releases the engagement by moving the pair of rotors apart from each other when placed at a second rotating position wherein: the releasing body is provided with two contact portions spaced apart in a direction of a relative rotation with respect to the other rotor; and the other rotor is provided with a moving portion that moves between the two contact portions in association with a relative rotation with respect to the releasing body, the moving portion allowing the releasing body to rotate to the first and second rotating positions with respect to the either one of the rotors by touching the two contact portions, respectively.
 2. The angle adjusting device according to claim 1, wherein: one of the either one of the rotors and the releasing body is provided with a convex portion on an opposite surface to the other of the either one of the rotors and the releasing body; and the other is provided with, on an opposite surface to the one of the either one of the rotors and the releasing body, a recess that engages with the convex portion when the releasing body is placed at the first rotating position, the convex portion moving the one of the either one of the rotors and the releasing body apart from the other by touching the opposite surface of the other except for the recess when the releasing body is placed at the second rotating position.
 3. The angle adjusting device according to claim 1, wherein the axis of rotation is composed of a rivet.
 4. The angle adjusting device according to claim 1, wherein the spring is a spiral spring.
 5. The angle adjusting device according to claim 1, wherein: each of the engaging portions is shaped into a triangle including the opposing surface of either rotor where each is provided when seen on a cross section in a radius direction of a rotation of the rotor; and either one of side portions of the triangle other than a side on the opposing surface of either rotor engages with a corresponding side portion of the engaging portion on the other rotor.
 6. The angle adjusting device according to claim 5, wherein the either one of side portions is tilted by a predetermined angle toward an engaging direction from the opposing direction.
 7. The angle adjusting device according to claim 1, wherein each of the engaging portions is formed by cutting and bending a part of either rotor where each is provided.
 8. The angle adjusting device according to claim 1, wherein the plurality of engaging portions are aligned in more than one line at radially different positions of each rotor where the plurality of engaging portions are provided.
 9. The angle adjusting device according to claim 1, wherein different intervals are given to the plurality of engaging portions in a direction of a rotation between the pair of rotors.
 10. The angle adjusting device according to claim 1, wherein at least one of the pair of rotors is provided with a coupling portion for coupling to a bar or tube member.
 11. The angle adjusting device according to claim 10, wherein the coupling portion is cylindrical.
 12. The angle adjusting device according to claim 10, wherein at least one of the pair of rotors is formed as an integral part of the coupling portion.
 13. The angle adjusting device according to claim 1, wherein at least one of the pair of rotors is provided with a cover that covers, at least partially, the plurality of engaging portions from an outside in a radius direction of a rotation.
 14. The angle adjusting device according to claim 13, wherein at least one of the pair of rotors and the cover are formed as one body.
 15. The angle adjusting device according to claim 1, wherein at least one of the pair of rotors is provided with a cover that entirely covers the plurality of engaging portions from an outside in a radius direction of a rotation.
 16. The angle adjusting device according to claim 15, wherein at least one of the pair of rotors and the cover are formed as one body.
 17. An angle adjusting device capable of adjusting a relative rotating position of a pair of rotors coupled through an axis of rotation step by step, comprising: a pair of rotors; a plurality of engaging portions provided on opposing surfaces of the pair of rotors opposing in a direction along the axis of rotation; and a spring for pushing the pair of rotors in an opposing direction, wherein at least one of the pair of rotors and the plurality of engaging portions are formed out of synthetic resin as one body. 